Probe adjustment tool and method of using same

ABSTRACT

A tool is disclosed for adjusting the tilt of a stylus in a probe. The tool includes a pair of arcuate caliper arms having inwardly directed pins for engaging openings in a pair of beveled washers extending between opposing faces of the probe housing and an adapter. In the disclosed method, the tool is then moved about the circumference of the probe until a given tool portion is generally in line with the direction of the tilt of the stylus. Then, the tool is used to move the pins toward each other to cause relative rotation of the washers to thereby bring the axis of the stylus into a desired orientation.

DESCRIPTION

1. Cross-Reference to Related Application

This is a division of application Ser. No. 504,149, filed June 14, 1983,now U.S. Pat. No. 4,510,693 issued Apr. 16, 1985, which is acontinuation-in-part of U.S. Ser. No. 388,187, filed June 14, 1982entitled "Touch Probe" (now U.S. Pat. No. 4,451,987 and assigned to theassignee of the present invention.

2. Technical Field

This invention relates to workpiece inspection systems and, moreparticularly, to the use of probes in automated machine tools to contactthe workpiece and provide information relating thereto.

3. Background Art

Automated machine tool systems require a precise means of locatingsurfaces on workpieces. One of the most common methods of accomplishingthis task is to have the machine move a probe into contact with theworkpiece and to record the probe position when contact is made. Probesof this type are known as touch probes. They generally include a stylusfor contacting the workpiece and circuitry which operates to generate anelectrical signal when the stylus contacts the part. A machinecontroller can calculate information about the shape or location of thepart from the X, Y and Z axes positional data of the probe when thestylus contact generates the electrical signal. Probes of this generalconfiguration have also been used to perform dimensional gaugingoperations where the displacement of the stylus is used to providegauging information.

The patent literature discloses several probe designs which are adaptedto be used in automatic machining centers where the probes aretemporarily stored in a tool magazine and are connected and removed fromthe spindle by an automatic tool changer mechanism. Representativeexamples of this general type are disclosed in U.S. Pat. No. 4,339,714to Ellis; U.S. Pat. No. 4,118,871 to Kirkham; U.S. Pat. No. 4,328,623 toJuengel et al; U.S. Pat. No. 4,153,998 to McMurtry; and U.S. Ser. No.259,257 entitled "Apparatus for Detecting the Position of a ProbeRelative to a Workpiece", filed Apr. 30, 1981 by Juengel (now U.S. Pat.No. 4,401,945) which is assigned to the assignee of this invention.

In general, the probe assemblies include a main body or housing in whichan end thereof opposite the stylus is connected to a suitable adapter.The adapter allows the probe housing to be incorporated into anautomated machine tool in the same way as a typical cutting tool. Theadapters vary in configuration depending upon the machine tool in whichthe probe is to be utilized. The adapters can also be configured toenable the probe to be used with a hand or gripping element of anautomaton, such as an industrial robot.

It is important that the proper location and orientation of the stylusbe provided in order for the probe to generate accurate data. Forexample, it is often imperative that the tip of the stylus and itsassociated shaft be precisely centered with the axis of the spindledrive when the probe is used in a machining center. In the past, suchprecision was attempted to be achieved by maintaining strict tolerancesor using special procedures during the construction of the probe.However, such precautions were not always adequate and, in any event,they increased the manufacturing costs of the probe assembly. Knownprobe constructions (such as the probes sold by Renishaw Electrical Ltd.and the assignee of the present invention) have included provision forcentering the tip of the stylus by adjusting the tilt of the probe headwhich rests on a spherical seat. However, this technique can introduce acorresponding tilt on the stylus shank thereby limiting the usefulnessof the probe in some measuring operations.

DISCLOSURE OF THE INVENTION

The general objective of the present invention is to provide a probeassembly with convenient means of adjusting the position of the stylus.

According to the teachings of this invention the probe housing oppositethe stylus is provided with a projecting member which is inserted withinan opening or well formed in an opposing face of the adapter. Therelative dimensions of the well and member are such that the probehousing may be shifted laterally with respect to the major axis of theadapter. Provision is made for contacting the sides of the member andmoving the probe housing in the radial direction so as to position thestylus at the desired location. Preferably, the member is frusto-conicalin shape with its sides diverging towards the adapter. The adjustmentmeans takes the form of set screws which extend tranversely through theadapter and contact the diverging sides of the member. In such manner,the probe housing is drawn axially towards the adapter and securedthereto in addition to shifting the probe housing radially as defined bythe extent of protrusion of the set screws into the well. In thepreferred embodiment, three equally spaced set screws are utilized andthey are opposed by spring loaded plungers. The plungers serve toprevent accidental separation of the probe housing from the adapter inthe event that the set screws are not in operable engagement with themember.

According to another feature of this invention, a pair of beveledwashers having non-parallel surfaces are mounted between the probehousing and the adapter. The washers are adapted to be rotated withrespect to each other to thereby adjust the tilt of the probe housingand thus adjust the orientation of the stylus axis. Stylus adjustment ofthis type is made according to the preferred embodiment by includingholes in the peripheral surfaces of the washers. A tool having arcuatecaliper legs is used to engage the washer holes. Means are provided inthe tool for moving the caliper legs about an arcuate path so as tocontrol movement of the washers and bring the stylus axis into properorientation.

BRIEF DESCRIPTION OF THE DRAWINGS

Still other features and advantages of the present invention will becomeapparent to one skilled in the art after reading the followingspecification and by reference to the drawings in which:

FIG. 1 is a front elevational view with parts in cross-section of aprobe assembly made in accordance with the teachings of this invention,the probe assembly being shown mounted in a spindle head of a machiningcenter;

FIG. 2 is an exploded perspective view of the probe assembly;

FIG. 3 is a cross-sectional view taken along the lines 3--3 of FIG. 1;

FIG. 4 is a fragmentary cross-sectional view illustrating an alternativelocation for a proximity switch in the adapter;

FIG. 5 is a perspective view of a tool used to adjust the tilt of thestylus according to one feature of this invention;

FIG. 6 is a cross-sectional view taken along the lines 6--6 of FIG. 5;

FIG. 7 is a partial cross-sectional view taken along the lines 7--7 ofFIG. 6;

FIG. 8 is a simplified elevational view of the probe assembly showingthe stylus in a tilted orientation;

FIG. 9 is a view taken along the lines 9--9 of FIG. 8; and

FIG. 10 is a view similar to that of FIG. 9 after the stylus has beenadjusted.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to FIGS. 1-3 the probe assembly 10 consists generally ofthree parts: a stylus 12, a probe housing 14 and an adapter 16. Theprobe housing 14 is more specifically made up of a cylindrical switchunit 18 and a cylindrical circuit unit 20 which are connected together,the end of circuit unit 20 being closed off by a specially formed plate22 which will be described in detail.

The probe housing 14 is adapted to be detachably connected to a varietyof different adapters whose configurations, especially the shanks, aredesigned to be used with different machine tools. In FIG. 1, the probeassembly 10 is shown mounted in a spindle head 24 of a numericallycontrolled machining center. The shank of the adapter is tapered andincludes a threaded bore 26 therein for receiving a motor driven screw(not shown). The adapter may further include a flange portion 28 with anannular ring for engaging one or more drive keys 30.

The probe housing may include a plurality of light emitting diodes 32for transmitting information relating to the status of the probe back toa remote receiver head. Probe transmission circuitry within unit 20receives power from batteries 34, 36 slideably received therein and heldin place by cap 38.

The switch unit 18 includes a plurality of contacts mechanicallyarranged so as to reflect movement of probe stylus 12 resulting from itcontacting another object such as a workpiece surface. The mechanicalarrangement of this construction is now shown in detail herein, but sucharrangements are known to those skilled in the art and are disclosed,for example, in the parent application Ser. No. 388,186 (now U.S. Pat.No. 4,451,987) referred to above. Briefly, the switch unit includes ashaft 40 to which stylus 12 is removable connected as by way of setscrew 42. A diaphram 43 seals the interior of the switch unit 18 fromadverse environmental conditions. The opposite end of shaft 40 isconnected to a follower or wobble plate 44. Wobble plate 44 carries aplurality of conductive inserts 46 which are normally urged againstcorresponding balls 48 by the action of spring 50. However, when thestylus 12 moves from its rest position the wobble plate 44 follows thestylus motion lifting up one of the inserts 46 from its correspondingball contact which is fixed. The pairs of ball-switch elements formelectrical contact switches whose change in resistance or otherelectrical characteristics is monitored by the circuitry within unit 20and transmitted via LED's 32 to the machine controller.

It should be noted that at this point that the description of the probeso far described is merely for purposes of illustrating the environmentin which the stylus adjustment features of the present invention may beincorporated.

The reader's attention is particularly drawn towards the area ofconnection between the probe housing 14 and adapter 16. Adapter 16includes a generally flat end face 50 having an opening or well 52formed therein. in this embodiment, the end face 50 is part of an outerannular flange portion 54 of substantial thickness forming a pedestalwhich is connected to the remainder of adapter 16 through a neck 56.

The end face 58 of probe housing plate 22 includes a member 60projecting therefrom. Member 60, has a radial dimension that is lessthan that of adapter well 52. Preferably member 60 has a frusto-conicalshape in which the sides thereof diverge towards adapter 16. By way of aspecific but non-limiting example, well 52 has a diameter of 1.460inches, whereas the outermost extremities of member 60 has a diameter of1.360 inches. Member 60 is adapted to be inserted into well 52 as can beseen most clearly in FIG. 1. Due to the differences in cross-sectionaldimension between well 52 and member 60, there is a certain amount ofclearance therebetween. This clearance allows for the lateral adjustmentof probe stylus 12.

The adapter flange 54 includes radial adjustment devices in the form ofthree equally spaced set screws 62, 64 and 66 threadably mounted inbores 74, 76 and 78 respectively. The outer ends of screws 62-66 includesockets or other means therein to enable the user to use a tool such asa socket wrench (not shown) to drive the rounded ends of the screwsagainst the sides of member 60.

Assume, for example, that the stylus 12 is in the position shown inphantom lines in FIG. 1 and it is desired to bring the tip 62 thereofinto concentric alignment with the major longitudinal axis of adapter16. It should be understood that the probe is shown out of alignment inan exaggerated manner for purposes of illustrating the operation of theinvention. To bring the probe tip 62 into alignment, the operatorrotates the appropriate set screws 62-66 to press against the sides ofmember 60 thereby moving the housing 14 in the radial direction untilthe tip 62 is at the desired location. The diverging sides of member 60provide a ramping action when the screws are tightened. Tightening ofthe screws thus also urge housing 14 in an axial direction towards theadapter 16 to thereby lock the adjusted stylus tip 62 in place.

The adapter flange 54 also advantageously employs a plurality ofspring-loaded plungers 68, 70 and 72 which are threadably mounted inbores 80, 82 and 84 respectively. The purpose of plungers 68-72 is toprovide sufficient inward force on the sides of member 60 to preventaccidental separation of the probe housing from adapter 16 in the eventthat the set screws 62-66 do not serve this purpose. For example, ifduring the alignment process the operator backs-off the set screws theprobe housing 14 would otherwise fall from the adapter 16 creating thepotential for damage to the sensitive components in the probe housing14. This is prevented by way of the resilient plunger heads. The plungerheads move outwardly when the member 60 is first inserted into theadapter well 52 but move back inwardly to engage the diverging sides ofthe member to prevent axial separation.

The foregoing construction provides lateral positioning of the stylustip 62, i.e. in a direction transverse to the major longitudinal axis ofthe adapter 16. The following feature of this invention may optionallybe incorporated into the probe construction to enable the user to adjustthe tilt of the stylus 12. For example, it is generally desirable tobring the axis of the stylus into a concentric relationship with theaxis of the adapter thereby centering it with the axis of rotation ofthe machine tool. In FIG. 8 the axis 90 of stylus 12 is shown in anexaggerated manner tilted with respect to the adapter axis 92. It shouldbe noted that the axis 92 generally corresponds with the major axis ofprobe housing 14 but that the later may in actuality be shifted somewhatduring the lateral adjustment process. It is the alignment of the styluswith the machine spindle head that is important so that somemisalignment of the intermediate probe housing 14 can be tolerated.

To adjust the tilt of the stylus axis, a pair of washers 94 and 96 aredisposed between the mutually opposing faces of adapter 16 and probehousing 14. Washers 94 and 96 are formed with non-parallel opposingsurfaces as perhaps can be best seen in FIGS. 1 and 2. Washers of thistype are known in the art as beveled washers. The washers 94 and 96 arepiloted about an intermediate hub 98 formed on housing end plate 22. Thewashers are adapted to rotate circumferentially with respect to eachother about hub 98. When the thickest portion of one washer is axiallyaligned with the thinnest portion of the other washer, the two washerscooperate to provide generally parallel outer surfaces transverse to theelongate axis of the probe assembly 10. When the washers are rotatedfrom this position, however, the outer surfaces become inclined withrespect to each other. Since the outer surfaces of washers 94 and 96define the angular displacement of the probe housing 14 with respect toadapter 16 it is possible to adjust the tilt of the stylus axis 90 sincethe stylus axis will follow the angular displacement of the probehousing 14 defined by the washers 94, 96.

In FIG. 1 there is no angular displacement created because the washersare oppositely aligned, i.e., thickest portion of one washer beingaxially aligned with the thinnest portion of the other washer. The axisof the stylus 12 is also shown in FIG. 1 centrally aligned. This may bethe situation encountered during initial setup of the probe. However, asshown in FIG. 8 it is possible that the stylus axis 90 be tilted in thissituation. Pursuant to this feature of the invention, the stylus tiltcan be easily corrected merely by rotating washers 94, 96 with respectto each other to bring the stylus axis at least parallel with the axis92. Lateral adjustment of the stylus 12, if needed, can be accomplishedas described above or in other manners.

A tool 100 is shown in FIGS. 5-10 for rotating the washers and adjustingthe stylus tilt. Tool 100 includes a pair of arcuate caliper arms 102and 104. Each of the arms include inwardly directed pins 106 and 108 forengaging openings 110 and 112, respectively, radially extendingoutwardly from the thickest portions of washers 96 and 94, respectively.Tool 100 acts in a rack and pinion type manner to move arms 102, 104simultaneously to cause their respective pins 106, 108 to move in anarcuate path. The tool is constructed so that the distances between eachof the pins 106, 108 and a given point on the tool remains in a fixedrelationship. In this embodiment, pins 106, 108 always remain the samedistance from the axis of knob 114. Knob 114 is connected to a star-gear116 having teeth 118 radially extending therefrom. Diametricallyopposing teeth 118 each engage one of the series of holes 120 and 122 inarms 102 and 104, respectively. The arms are held in spaced relationshipby way of a pair of slots formed in opposing sides of gear housing 124.Slots 126 and 128 cooperate to hold arm 102 in a spaced relationshipwith arm 104 which is guided by way of slots 130 and 132.

In use, the tool 100 is adjusted so that pins 106 and 108 engage theopenings 110 and 122 in washers 94, 96. If not already in opposedrelationship, knob 114 is rotated until the pins 106 and 108 aregenerally diametrically opposite one another. Then, the gear housing 124is rotated circumferentially until the knob 114 is at a location pointedto by the tilted stylus 12 as can be seen most clearly in FIGS. 8 and 9.This procedure provides a reference point for the peak of the stylustilt since the openings 110 and 112 of the washers are located on thethickest parts thereof. Then, knob 114 is rotated as shown in FIG. 10 todraw the pins 106 and 108 towards the gear housing 124 until such timeas the stylus axis is properly aligned. The movement of pins 106 and 108operate to rotate the beveled washers 94 and 96 to thereby redefine theangular relationship between the outer surfaces of the washers.Non-planearity on the outer washer surfaces cause the probe housing 14to tilt with respect to adapter 16 and bring the axis 90 of stylus 12into parallel relationship with axis 92. If the stylus tip 62 does notlie on the desired axis 92, then the user may use the set screws 62-66to laterally position the stylus as described above. Tightening of theset screws urges the probe housing 14 against the adapter 16 therebyclamping the beveled washers in their adjusted angular positions.

A probe of the type illustrated in these drawings is normally loadedinto the spindle head 24 by an automatic tool change mechanism (notshown). The adapter 16 advantageously employs a proximity or limitswitch that changes its electrical characteristics when the probe 10 isinserted into the spindle head 24. In FIG. 1, a limit switch 140includes a plunger 142 that is urged inwardly when the adapter 16 isinserted into the spindle head 24. Alternatively, switch 140' mayinclude a plunger 142' which is pressed in by the drive keys 30 wheninserted as shown in FIG. 4. In both embodiments, the output of theswitch is connected to circuitry contained within unit 20 of probehousing 14. In FIG. 1 this circuitry is schematically illustrated asbeing mounted on a circuit board 144. In the preferred embodiment,activation of the switch operates to couple energy from the batteries34, 36 to the circuitry, which in turn, responds by driving LED's 32 ata given frequency. In such manner, the machine controller (not shown)knows that the probe is operating properly and is ready to perform aprobing operation. Once the stylus 12 contacts an object such as aworkpiece, the circuitry operates to shift the frequency of theradiation transmitted by LED's 32 to thereby indicate contact.

Electrical connection between switch 140 or 140' and circuitry board 144is provided by way of wires 146, 148 which are connected to the ends ofpin connectors 150 and 152. Pin connectors 150 and 152 havespring-loaded heads which enable them to be yieldable in the axialdirection. The heads 150 and 152 are urged against concentric conductiverings 154 and 156, respectively, formed on the end face of member 60 ascan be seen most clearly in FIG. 2. Thus, the pins and conductive ringsoperate to form a separable electrical connection between adapter 16 andprobe housing 14. The conductive rings may be connected to suitablelocations on circuit board 144 by appropriate means (not shown) such aswires extending through probe housing unit 20.

It should be understood that the foregoing description contains specificexamples of various features of this invention which may be usedindividually if desired but when combined cooperate to provide anextremely versatile probe construction. Various modifications of thespecifically illustrated examples will become apparent to those skilledin the art upon a study of the specification, drawings and followingclaims.

I claim:
 1. A tool for use in adjusting a probe assembly including apair of beveled washers adapted to be rotated with respect to each otherto adjust the tilt of a stylus extending from one end of a probehousing, said tool comprising:a pair of arcuate caliper arms, each armhaving inwardly directed pins for engaging openings in the washers, andmanually adjustable means for engaging the arms and simultaneouslymoving said pins relative to each other to thereby rotate the washers.2. The tool of claim 1 wherein said arms include a series of holestherein and said means includes a gear having radially projecting teeth,diametrically opposing teeth being operative to engage the holes in eachof the arms, and a knob for rotating the gear.
 3. A method of adjustingthe tilt of the stylus in a probe assembly having a pair of beveledwashers extending between opposing faces of a probe housing and anadapter, said method comprising the steps of:engaging holes in thethickest peripheral portion of each washer with pins formed on caliperarms of an adjustment tool, said tool including a portion connected tothe arms and spaced equidistant from each of the pins; moving said toolabout the circumference of the probe until the tool portion is generallyin line with the direction of the tilt of the stylus; and using the toolto move the pins toward each other to cause relative rotation of thewashers to thereby bring the axis of the stylus into a desiredorientation.